1. Field of the Invention
The present invention relates to a double twist machine for manufacturing multi-stranded electrically conductive wires, such as electrically conductive wires for automobiles, appliances and so forth, and more particularly to a method and apparatus for manufacturing compact conductors.
2. Statement of the Prior Art
In manufacturing compact conductors with a conventional double twist machine 1a (see FIG. 4) in which a compacting die 4a and a converging die 4b are respectively provided on the inlet sides of a drawing device 6a and the double twist machine 1a, concentric conductors of a single-layer structure can be compacted through one process, while concentric conductors of a multi-layer structure must be compacted on a one-compaction-for-one layer basis through a plurality of processes.
A double twist compact conductor manufacturing machine having a strander upstream of a drawing device is disclosed in Japanese Patent Public Disclosure Nos. 160515/1985 and 129704/1983.
However, the above-mentioned prior art double twist machine 1a has difficulties in leading a wire through the compacting die 4a. On top of this, in a case where a defect such as strand separation or the like takes place in a twisted wire at a position prior to the compacting die 4a, the wire will break when it reaches the compacting die 4a.
This problem of wire breakage also takes place with concentric twisted wire with a multi-layer structure when the same are compacted through only one process. This is because it is impossible to exert uniform pressure on all the constituent strands of the wire when put through a single compaction, and hence strand separation takes place in the wire at the entry of the compacting die 4a, resulting in breakage of the wire. This problem can be solved by compacting the twisted wire on a layer-by-layer basis through two processes, but this type of manufacturing method reduces production efficiency.
In addition, the construction of the prior art drawing devices was complicated.